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Discussion Starter #1
Hey All,

Just to give you some background.... When i purchased the car the motor had a light tapping when accelerating, didnt think much of it..

I just this morning redid the timing on the 302. The problems that im having is...

1. The Motor has a REALLY load Rattling sound from the motor when you accelerate. Especialy when traveling up hills. if you speed up going down a hill, it doesnt do it. Ideas?

2. The Thing Idle's really High in Park. like ive tried to lower it by ajusting the idle speed but all the way out doesnt do anything. its a Thermoquad. If anyone is interested the idle mixture screws are 6 turns out. any and it cuts out.

HELP??!
 

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Discussion Starter #2
Oh yea, ONLY does it when your driving, i could thrash the shit out of the motor while its in P or N and its standstill and you dont hear it at all.
 

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Is it tapping or a deeper bumping. Last time this happened to me (I had just bought the car from an auction - no test drive) the crank mains where well and truly rooted. New crank thankyou very much.

This made a deep bumping noise under load only, not nice stuff!
 

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slikxb
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you gotta track it down. Top end or bottom end? Front or Back of motor? Put it in drive rest on the brakes and put it under load, this will hopefully produce said noise, then track it down.
Exhuast leaks can sound like this.
So can nackerd lifters.
 

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Thats detonation (pinging) that you can hear, I've got the same problem with my LTD. Check your timing (I bet its fine) and fill up with high octane fuel and see if that helps. At the moment I've tried adjusting my carb, reducing my timing a few degrees and using a fuel additive (Moreys) to no avail.
Make sure your engine isnt overheating as this can bring on pinging too. I dont know Thermoquads at all but 6 turns out seems a long way, most Holleys are set around 1.5 turns each.
Keep me posted on what you try cos I'm ready to give up.
 

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Yep - definately pinging! - and yes, it will only be evident when the motor is under load, going up hills, or foot to floor when you should be in a lower gear or hard acceleration. Thats why it doesn't happen in P or N free revving it.

Get a timing light and check your timing, as previously mentioned, 6 deg advanced is a good starting point. Having the timing too far advanced will also cause your engine RPM to idle too high.

1 - Set your timing
2 - adjust your FAST IDLE screw (connectd to throttle plate) ~7-800rpm
3 - adjust your mixture screw(s) - to get highest rpm - then readjust fast idle screw etc.

Then check timing again to make sure its still accurate.

If your engine starts to stall when winding the timing back - adjust the fast idle screw to increase rpm.

When on empty, try filling up using a tank of BP Ultimate 98 octane fuel (put in a valve protector addative) - should make a big difference.

Cheers
 

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Discussion Starter #9
yea Im running Optimax at the moment. Yea Im going to get a timing light today. BTW what is this notch that i can feel when i turn the distributor?
 

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BSR Twin System (tm)
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Yep, sounds like Pinging. As the other guys said, check your timing, and make sure you use some decent fuel. If you still have the problem, the advance curve in your distributor could be the problem.
 

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Discussion Starter #11
Ok Now,

Does anyone know how many turns out the Carter carby should be? because i have it at like 4 turns out now and ajusted the Curb idle (idle Solonoid) up so it would idle around 600-700. As specified on the car. The problem ive got now is that its Revving WAY TO HIGH when driving.

Does anyone out there who also has a ZH or has the same XC '79 motor could they tell me there settings please? im going out of my mind here
 

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There are no "correct" settings, or number of turns. Approx 2/12, very approx..

A lean mixture will also induce pinging. Possibly your EGR plate has corroded through leaking exhaust into the inlet manifold. This could explain the poor idle quality and extreme pinging under load.

Remove the carb and EGR plate and inspect the EGR for break-through from the exhaust passage.
 

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Discussion Starter #13
ok ive set the idle Mixture screws to "roughly" 2 turns out and set the fast idle screw. The car now seems to idle better and accelerate. This may seem dumb but... By screwing the idle mixture in, am i making it ritch or lean? also When i Turn the Dizzy i feel a Notch when turning like 1/2 way, its that a marker to tell you that your exactly 1/2 way?
 

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Turning the mixture screws clockwise = lean anticlockwise = richer. Generally turn them in until the idle slows down then back them off 1-2 turns, for a rough setting.

Don't know any notch when turning the dizzy, there is no half way mark, is it catching on somthing?
 

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The only notch I know of is one that locates the cap to the dizzy housing. Are you turning the whole dizzy or just the cap?. There is a 9/16 bolt near the base of the dizzy that you need to loosen before you turn the dizzy and make sure the cap is installed and secured properly, you'll know when its located properly when its sitting in the notch.
 

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Hey ZH did you fix your timing? I found the problem with mine. It was a blown head gasket between cyl 2 and3, its been developing over the last couple of hundred K's and I picked it up on a compression test.
Now the hard bit is fixing the problem without talking myself into a full rebuild :)
 

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I had the same thing years ago on a 302 in my old XT. It actually blew thru the gaskits on both cylinder banks - between centre 2 cyclinders - and the flame would just leap across cyclinders! That was my introduction to pinging - could you believe that one mechanic thought I had a cracked piston!!

Go the full rebuild there Nod!!!.........but you can also fix the head gaskits in a day. A good instruction manual, socket set and a torque wrench!! Dive off the deep end and get your fingers dirty!! Taking the heads off looks complex but is suprisingly easy. Even if you think it's just one head gaskit, replace them both.

Best tip - it's easy to pull apart!!! But LABEL parts with masking tape as pull 'em off!! Helps big time when you put it back together;)

Good luck!
 

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Thanks for the advice Trublu, I've done a few rebuilds before so I'm pretty familiar with what happens when you dont label things :). I now video the engine bay at various stages of the pulldown in case I forget where the pipes and brackets go. I've pulled the heads and decided to remove the block because it'll be much easier to put back together on the stand and stick back in in one piece.
 
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